As the title implies, should I do it? I love Arch so far, and I can fix most issues that pop out. However, I sometimes wish to start fresh without too much hassle, but I get a feeling NixOS isn't as mature as Arch.
Have any of you used both, and if so, what do you miss from Arch? What are you grateful for in NixOS?
Your reason of "wish to start fresh" doesn't sound compelling.
Arch is stable, and works great. Biggest draw for NixOS is packages. I don't think NixOS has anything to offer in packages that I can't get in Arch. I'll not advocate switching to an experimental distro with who knows what other headache, just because I can run Debian or rpm packages. Not for a daily driver.
I think the biggest draw for Nix is configuration.nix and being able to centralize your system configuration. I personally find the AUR to be better in terms of software, especially from GitHub.
I agree that people shouldn't jump blind into Nix without first getting to grips with it though a VM or something, tho. The learning curve is quite steep.